<?php
defined('BASEPATH') OR exit('No direct script access allowed');

/**
 * Creates a consistent, one-way snapshot from a legacy database and upgrades
 * it in an empty target database. It never writes to the source database.
 */
class DatabaseSyncService
{
    private $CI;
    private $sourceConfig;
    private $targetConfig;

    public function __construct()
    {
        $this->CI =& get_instance();
        $this->sourceConfig = $this->readConfig('DBSYNC_SOURCE');
        $this->targetConfig = $this->readConfig('DBSYNC_TARGET');

        if ($this->sourceConfig['host'] === $this->targetConfig['host']
            && $this->sourceConfig['port'] === $this->targetConfig['port']
            && $this->sourceConfig['database'] === $this->targetConfig['database']) {
            throw new RuntimeException('Database sumber dan target tidak boleh sama.');
        }
    }

    public function check()
    {
        list($source, $target) = $this->connectPair();
        try {
            $result = array(
                'status' => true,
                'source' => $this->databaseInfo($source, $this->sourceConfig['database']),
                'target' => $this->databaseInfo($target, $this->targetConfig['database']),
            );
            $result['target']['is_empty'] = $result['target']['objects'] === 0;
            return $result;
        } finally {
            $source->close();
            $target->close();
        }
    }

    public function snapshot()
    {
        list($source, $target) = $this->connectPair();
        $target->close();
        try {
            $path = $this->createSnapshot($source);
            return array(
                'status' => true,
                'backup' => $path,
                'size' => filesize($path),
                'sha256' => hash_file('sha256', $path),
            );
        } finally {
            $source->close();
        }
    }

    public function bootstrap()
    {
        // Both connections must succeed before the first target write.
        list($source, $target) = $this->connectPair();
        try {
            $targetInfo = $this->databaseInfo($target, $this->targetConfig['database']);
            if ($targetInfo['objects'] !== 0) {
                throw new RuntimeException(
                    'Bootstrap ditolak: target tidak kosong (' . $targetInfo['objects'] . ' objek).'
                );
            }

            $backup = trim((string) getenv('DBSYNC_BACKUP_FILE'));
            if ($backup === '') {
                $backup = $this->createSnapshot($source);
            } elseif (!is_file($backup) || !is_readable($backup)) {
                throw new RuntimeException('File backup tidak ditemukan atau tidak dapat dibaca.');
            }

            $expectedHash = strtolower(trim((string) getenv('DBSYNC_BACKUP_SHA256')));
            $actualHash = hash_file('sha256', $backup);
            if ($expectedHash !== '' && !hash_equals($expectedHash, strtolower($actualHash))) {
                throw new RuntimeException('Checksum backup tidak sesuai. Target belum diubah.');
            }
        } finally {
            $source->close();
            $target->close();
        }

        $sanitizedBackup = $this->sanitizeBackup($backup);
        try {
            $this->importBackup($sanitizedBackup);
            $this->runTargetMigrations();
            $verification = $this->verify();
        } finally {
            if (is_file($sanitizedBackup)) {
                @unlink($sanitizedBackup);
            }
        }

        return array(
            'status' => true,
            'message' => 'Snapshot legacy berhasil dimuat dan struktur target berhasil dimodernisasi.',
            'backup' => $backup,
            'backup_sha256' => $actualHash,
            'verification' => $verification,
        );
    }

    public function verify()
    {
        list($source, $target) = $this->connectPair();
        try {
            $required = array('accounts', 'users', 'journals', 'journal_details', 'items', 'item_barcodes');
            $missing = array();
            foreach ($required as $table) {
                if (!$this->tableExists($target, $this->targetConfig['database'], $table)) {
                    $missing[] = $table;
                }
            }
            if ($missing) {
                throw new RuntimeException('Verifikasi gagal, tabel wajib tidak tersedia: ' . implode(', ', $missing));
            }

            $latestFileVersion = $this->latestMigrationVersion();
            $migrationVersion = 0;
            if ($this->tableExists($target, $this->targetConfig['database'], 'migrations')) {
                $row = $target->query('SELECT COALESCE(MAX(version), 0) AS version FROM migrations')->fetch_assoc();
                $migrationVersion = (int) $row['version'];
            }

            $invalidAccounts = (int) $target->query(
                "SELECT COUNT(*) AS total FROM accounts WHERE kode_akun IS NULL OR kode_akun NOT REGEXP '^[0-9]{4}$'"
            )->fetch_assoc()['total'];
            $journal = $target->query(
                'SELECT COALESCE(SUM(debit),0) AS debit, COALESCE(SUM(kredit),0) AS kredit FROM journal_details'
            )->fetch_assoc();
            $journalDifference = round((float) $journal['debit'] - (float) $journal['kredit'], 2);

            $orphans = array(
                'journal_details' => $this->scalar($target,
                    'SELECT COUNT(*) FROM journal_details d LEFT JOIN journals j ON j.id=d.journal_id WHERE j.id IS NULL'),
                'invoice_details' => $this->tableExists($target, $this->targetConfig['database'], 'invoice_details')
                    ? $this->scalar($target,
                        'SELECT COUNT(*) FROM invoice_details d LEFT JOIN invoices i ON i.id=d.invoice_id WHERE i.id IS NULL')
                    : 0,
                'item_barcodes' => $this->scalar($target,
                    'SELECT COUNT(*) FROM item_barcodes b LEFT JOIN items i ON i.id=b.item_id WHERE i.id IS NULL'),
            );

            $passed = $migrationVersion === $latestFileVersion
                && $invalidAccounts === 0
                && abs($journalDifference) < 0.01
                && array_sum($orphans) === 0;

            if (!$passed) {
                throw new RuntimeException('Verifikasi target gagal. Periksa hasil audit sebelum cutover.');
            }

            return array(
                'status' => true,
                'migration_version' => $migrationVersion,
                'latest_migration_file' => $latestFileVersion,
                'account_codes_invalid' => $invalidAccounts,
                'journal_debit' => (float) $journal['debit'],
                'journal_credit' => (float) $journal['kredit'],
                'journal_difference' => $journalDifference,
                'orphans' => $orphans,
                'target' => $this->databaseInfo($target, $this->targetConfig['database']),
            );
        } finally {
            $source->close();
            $target->close();
        }
    }

    private function readConfig($prefix)
    {
        $config = array(
            'host' => trim((string) getenv($prefix . '_HOST')),
            'port' => (int) (getenv($prefix . '_PORT') ?: 3306),
            'username' => trim((string) getenv($prefix . '_USERNAME')),
            'password' => (string) getenv($prefix . '_PASSWORD'),
            'database' => trim((string) getenv($prefix . '_DATABASE')),
        );

        foreach (array('host', 'port', 'username', 'password', 'database') as $key) {
            if ($config[$key] === '' || $config[$key] === 0) {
                throw new RuntimeException('Konfigurasi ' . $prefix . '_' . strtoupper($key) . ' belum lengkap.');
            }
        }
        return $config;
    }

    private function connectPair()
    {
        $source = $this->connect($this->sourceConfig, 'sumber');
        try {
            $target = $this->connect($this->targetConfig, 'target');
        } catch (Throwable $exception) {
            $source->close();
            throw $exception;
        }
        return array($source, $target);
    }

    private function connect($config, $label)
    {
        mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);
        $connection = mysqli_init();
        $connection->options(MYSQLI_OPT_CONNECT_TIMEOUT, 10);
        try {
            $connection->real_connect(
                $config['host'],
                $config['username'],
                $config['password'],
                $config['database'],
                $config['port']
            );
            $connection->set_charset('utf8mb4');
            return $connection;
        } catch (Throwable $exception) {
            throw new RuntimeException('Koneksi database ' . $label . ' gagal. Proses dihentikan.', 0, $exception);
        }
    }

    private function databaseInfo($connection, $database)
    {
        $statement = $connection->prepare(
            'SELECT COUNT(*) AS total FROM information_schema.tables WHERE table_schema=?'
        );
        $statement->bind_param('s', $database);
        $statement->execute();
        $objects = (int) $statement->get_result()->fetch_assoc()['total'];
        $statement->close();

        return array(
            'database' => $database,
            'server_version' => $connection->server_info,
            'objects' => $objects,
        );
    }

    private function tableExists($connection, $database, $table)
    {
        $statement = $connection->prepare(
            'SELECT COUNT(*) AS total FROM information_schema.tables WHERE table_schema=? AND table_name=?'
        );
        $statement->bind_param('ss', $database, $table);
        $statement->execute();
        $exists = (int) $statement->get_result()->fetch_assoc()['total'] > 0;
        $statement->close();
        return $exists;
    }

    private function createSnapshot($source)
    {
        $directory = trim((string) getenv('DBSYNC_BACKUP_DIRECTORY'));
        if ($directory === '') {
            $directory = dirname(FCPATH) . DIRECTORY_SEPARATOR . 'private_backups' . DIRECTORY_SEPARATOR . 'accounting_dev';
        }
        if (!is_dir($directory) && !mkdir($directory, 0700, true)) {
            throw new RuntimeException('Folder backup tidak dapat dibuat.');
        }
        $path = rtrim($directory, '/\\') . DIRECTORY_SEPARATOR
            . $this->sourceConfig['database'] . '-cutover-' . date('Ymd-His') . '.sql';
        $file = fopen($path, 'xb');
        if (!$file) {
            throw new RuntimeException('File snapshot tidak dapat dibuat.');
        }

        try {
            fwrite($file, "-- One-way database cutover snapshot\nSET NAMES utf8mb4;\nSET FOREIGN_KEY_CHECKS=0;\nSET UNIQUE_CHECKS=0;\n\n");
            $tables = array();
            $views = array();
            $result = $source->query('SHOW FULL TABLES');
            while ($row = $result->fetch_row()) {
                if (strtoupper($row[1]) === 'VIEW') {
                    $views[] = $row[0];
                } else {
                    $tables[] = $row[0];
                }
            }

            $source->query('SET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ');
            $source->query('START TRANSACTION WITH CONSISTENT SNAPSHOT, READ ONLY');
            foreach ($tables as $table) {
                $quotedTable = $this->identifier($table);
                $createRow = $source->query('SHOW CREATE TABLE ' . $quotedTable)->fetch_row();
                fwrite($file, 'DROP TABLE IF EXISTS ' . $quotedTable . ";\n" . $createRow[1] . ";\n\n");

                $selectColumns = array();
                $columnResult = $source->query('SHOW FULL COLUMNS FROM ' . $quotedTable);
                while ($column = $columnResult->fetch_assoc()) {
                    if (stripos((string) $column['Extra'], 'GENERATED') === false) {
                        $selectColumns[] = $this->identifier($column['Field']);
                    }
                }
                $rows = $source->query(
                    'SELECT ' . implode(',', $selectColumns) . ' FROM ' . $quotedTable,
                    MYSQLI_USE_RESULT
                );
                $columns = array();
                foreach ($rows->fetch_fields() as $field) {
                    $columns[] = $this->identifier($field->name);
                }
                $batch = array();
                while ($row = $rows->fetch_row()) {
                    $values = array();
                    foreach ($row as $value) {
                        $values[] = $value === null ? 'NULL' : "'" . $source->real_escape_string($value) . "'";
                    }
                    $batch[] = '(' . implode(',', $values) . ')';
                    if (count($batch) >= 200) {
                        $this->writeInsertBatch($file, $quotedTable, $columns, $batch);
                        $batch = array();
                    }
                }
                $rows->free();
                if ($batch) {
                    $this->writeInsertBatch($file, $quotedTable, $columns, $batch);
                }
                fwrite($file, "\n");
            }
            $source->commit();

            foreach ($views as $view) {
                $quotedView = $this->identifier($view);
                $create = $source->query('SHOW CREATE VIEW ' . $quotedView)->fetch_assoc();
                fwrite($file, 'DROP VIEW IF EXISTS ' . $quotedView . ";\n" . $create['Create View'] . ";\n\n");
            }
            fwrite($file, "SET UNIQUE_CHECKS=1;\nSET FOREIGN_KEY_CHECKS=1;\n");
        } catch (Throwable $exception) {
            @$source->rollback();
            fclose($file);
            @unlink($path);
            throw $exception;
        }

        fclose($file);
        @chmod($path, 0600);
        return $path;
    }

    private function writeInsertBatch($file, $table, $columns, $batch)
    {
        fwrite(
            $file,
            'INSERT INTO ' . $table . '(' . implode(',', $columns) . ") VALUES\n"
            . implode(",\n", $batch) . ";\n"
        );
    }

    private function sanitizeBackup($sourcePath)
    {
        $targetPath = tempnam(sys_get_temp_dir(), 'accounting-cutover-');
        $input = fopen($sourcePath, 'rb');
        $output = fopen($targetPath, 'wb');
        if (!$input || !$output) {
            throw new RuntimeException('File sementara untuk import tidak dapat dibuat.');
        }
        $sqlModeInjected = false;
        $generatedScheduleInsert = false;
        while (($line = fgets($input)) !== false) {
            $line = preg_replace('/\\sDEFINER=`[^`]+`@`[^`]+`/i', '', $line);

            // Older snapshots produced before this service included the
            // generated schedule_date column. MySQL only accepts DEFAULT for
            // generated values, so retain the row and let MySQL calculate it.
            if (stripos($line, 'INSERT INTO `k_employee_shift_schedules`') === 0
                && stripos($line, '`schedule_date`') !== false) {
                $generatedScheduleInsert = true;
            } elseif ($generatedScheduleInsert && isset($line[0]) && $line[0] === '(') {
                $line = preg_replace(
                    "/^(\\('[^']*','[^']*',(?:'[^']*'|NULL),'[^']*','[^']*'),(?:'[^']*'|NULL)(,)/",
                    '$1,DEFAULT$2',
                    $line
                );
                if (substr(rtrim($line), -1) === ';') {
                    $generatedScheduleInsert = false;
                }
            }
            fwrite($output, $line);
            // Legacy MySQL ENUM columns contain empty-string values that are
            // valid in the old data but rejected by modern strict SQL mode.
            // Compatibility mode preserves those rows; later migrations map
            // them to the modern representation without deleting data.
            if (!$sqlModeInjected && preg_match('/^SET NAMES /i', trim($line))) {
                fwrite($output, "SET SESSION sql_mode='NO_ENGINE_SUBSTITUTION';\n");
                $sqlModeInjected = true;
            }
        }
        fclose($input);
        fclose($output);
        return $targetPath;
    }

    private function importBackup($backup)
    {
        $mysql = trim((string) getenv('DBSYNC_MYSQL_BIN'));
        if ($mysql === '') {
            $mysql = 'C:\\xampp\\mysql\\bin\\mysql.exe';
        }
        if (!is_file($mysql)) {
            throw new RuntimeException('mysql client tidak ditemukan: ' . $mysql);
        }

        $command = array(
            $mysql,
            '--host=' . $this->targetConfig['host'],
            '--port=' . $this->targetConfig['port'],
            '--user=' . $this->targetConfig['username'],
            '--default-character-set=utf8mb4',
            '--database=' . $this->targetConfig['database'],
        );
        $this->runProcess($command, $backup, array('MYSQL_PWD' => $this->targetConfig['password']));
    }

    private function runTargetMigrations()
    {
        $environment = array(
            'DB_HOST' => $this->targetConfig['host'],
            'DB_PORT' => (string) $this->targetConfig['port'],
            'DB_USERNAME' => $this->targetConfig['username'],
            'DB_PASSWORD' => $this->targetConfig['password'],
            'DB_DATABASE' => $this->targetConfig['database'],
        );
        $this->runProcess(
            array(PHP_BINARY, FCPATH . 'index.php', 'migrate/latest'),
            null,
            $environment,
            FCPATH
        );
    }

    private function runProcess($command, $stdinFile = null, $environment = array(), $workingDirectory = null)
    {
        $descriptors = array(
            0 => $stdinFile ? array('file', $stdinFile, 'rb') : array('pipe', 'r'),
            1 => array('pipe', 'w'),
            2 => array('pipe', 'w'),
        );
        $processEnvironment = getenv();
        if (!is_array($processEnvironment)) {
            $processEnvironment = array();
        }
        foreach ($environment as $key => $value) {
            $processEnvironment[$key] = $value;
        }

        $process = proc_open($command, $descriptors, $pipes, $workingDirectory, $processEnvironment);
        if (!is_resource($process)) {
            throw new RuntimeException('Proses database tidak dapat dijalankan.');
        }
        if (!$stdinFile) {
            fclose($pipes[0]);
        }
        $stdout = stream_get_contents($pipes[1]);
        $stderr = stream_get_contents($pipes[2]);
        fclose($pipes[1]);
        fclose($pipes[2]);
        $exitCode = proc_close($process);
        if ($exitCode !== 0) {
            throw new RuntimeException(trim($stderr ?: $stdout ?: 'Proses database gagal.') . ' (exit ' . $exitCode . ')');
        }
        return trim($stdout);
    }

    private function latestMigrationVersion()
    {
        $versions = array();
        foreach (glob(APPPATH . 'migrations' . DIRECTORY_SEPARATOR . '*.php') as $file) {
            if (preg_match('/^(\\d+)_/', basename($file), $match)) {
                $versions[] = (int) $match[1];
            }
        }
        return $versions ? max($versions) : 0;
    }

    private function scalar($connection, $sql)
    {
        $row = $connection->query($sql)->fetch_row();
        return (int) $row[0];
    }

    private function identifier($value)
    {
        return '`' . str_replace('`', '``', $value) . '`';
    }
}